Agricultural work vehicles, such as tractors or combines or other agricultural harvesting machines, are known to tow implements that perform (or include tool bar(s) that perform) one or more functions, such as plowing, planting or seeding, fertilizing, and harvesting in a field. Also, it is known for agricultural work vehicles to employ one, two or more folding markers that typically are extendable beyond the perimeter of the work vehicle and create markings by, for example, gouging furrows in the field adjacent to the vehicle. Such markers are typically attached to the implement towed by the work vehicle, although they may be attached to the work vehicle itself. Since an agricultural work vehicle typically traverses a field in a systematic row-by-row format, the markers often are used to create markings in the field to indicate to the operator of the vehicle a path for the next row. Markers are often, though not necessarily, installed in pairs on both sides of an agricultural work vehicle. Also, some agricultural work vehicles include more than one marker that can extend from a given side of the vehicle. For example, an agricultural work vehicle can include both inner and outer markers, where the outer markers are employed to provide markings at relatively larger distances from the work vehicle, and the inner markers are employed to provide markings at relatively smaller distances from the work vehicle.
With respect to most agricultural work vehicles, it is necessary for the work vehicles to have the capability of raising and lowering the implements (or tool bars of the implements) and markers with respect to the work vehicles and the ground. For example, a typical agricultural work vehicle proceeding through a field in a row-by-row, or more commonly a multiple row-by-row, manner must turn around at the end of each row in order to proceed down the successive row. While turning around, it is sometimes appropriate to raise the implement (or the tool bar of the implement) towed by the agricultural work vehicle some distance above the ground to prevent the implement from acting upon (or damaging) the ground or crops outside the lines of the rows. Similarly, it is common that the markers attached to an implement of a work vehicle be raised some distance above the ground while the work vehicle is turning around to prevent improper marking, damage to the ground or crops, or damage to the markers themselves that might occur if the markers encountered obstacles such as fences, trees, and boulders.
Often it is necessary not only that the markers themselves be raised but also that the implementation of the markers be changed while the work vehicle is turning around. For example, while it may be appropriate to utilize markers on both sides of a work vehicle as it first enters and makes its initial crossing of a field so as to create row markings on both sides of the work vehicle, implementation of markers on both sides of the work vehicle is no longer appropriate once it has completed its first row. Instead, it is then appropriate to utilize a marker only on one side of the work vehicle so that, as the vehicle proceeds down one of the two paths marked during its initial crossing of the field, a new row marking parallel to the previous row markings is created only in that section of the field that has not yet been traversed by the work vehicle. Insofar as a work vehicle needs to turn around regularly as it advances row-by-row through a field, it is appropriate to alternate the implementation of the markers used to create row markings so that new row markings are always created in that section of the field that has not yet been traversed by the work vehicle.
Because it is often appropriate for the markers and implement/tool bar of an agricultural work vehicle to be raised and lowered at the same time, some conventional agricultural work vehicles actuate the raising and lowering of their markers and implements/tool bars using the same hydraulic valve. Such a single-valve system is simple and inexpensive to install on an agricultural work vehicle. However, in some agricultural work vehicles, it is desirable to have the capability of controlling the raising and lowering of markers independently of the raising and lowering of the implements/tool bars. For example, in the case of planters, it often is desirable to have the capability of raising and lowering markers, for reasons such as those discussed above (e.g., to avoid damage to the markers), without simultaneously raising and lowering the implements/tool bars of the planters, which would interrupt the planting operation. Some conventional planters, as well as other conventional agricultural work vehicles that need to provide such independent control of the markers and implements/tool bars, provide such independent control through the use of two (or more) different hydraulic valves for separately actuating the different devices.
Some of the challenges associated with modern marking systems are associated with the size of multi-row planters. Multi-row planters can extend a planting width of sixty feet, for example, or lesser or greater, with variable planting unit spacing of fifteen, twenty and thirty inches, or other spacing. Folding markers for a sixty foot wide planter therefore are required to extend thirty feet, for example, when marking. The length of the marker creates moment arm (foot-lbs.) and other self weight loading, which the folding marker must sustain while at the same time must be economical to manufacture. Additionally, if the folding marker hits an obstruction, additional moment arm (foot-lbs.) loading is created which is proportional to the length of the folding marker. Simply making a marker more heavier with stronger supports may be counter productive in that this can increase the self weight loading and also increase the operating expense of the planter as it now takes more fuel to tow the planter through the field.
The speed of raising and lowering the folding marker can also be a concern as a fast moving folding or unfolding operation may provide a high dynamic load on the marker, whereas a slow moving folding or unfolding operation may not be particularly tolerable by the operator.
Additionally, and as mentioned above, it is common for marker actuation to alternate as the operator makes successive turns at the ends of a field. Such alternation can complicate the operation of the agricultural implement if done manually. The raising and lowering of the folding marker can also be complicated by the length of the marker. The moment arm loading is also present during folding and unfolding of the marker, and it is important to avoid a runaway load situation during folding and unfolding of the marker.
Accordingly, what is needed in the art is a folding marker suitable for use with the large width agricultural planters, or other agricultural implements used therewith, which can sustain the loading associated with relatively large size of the marker while being economical to manufacture and operate. Additionally, it is desired that the folding marker can accommodate hitting an obstruction, without damaging the folding marker. Yet further, it is desired to avoid a runaway load situation during folding and unfolding of the marker, and make the alternating folding and unfolding of the marker be automatic.